Description

These routines are part of the RPC library which allows C language
programs to make procedure calls on other machines across the network.

These routines are associated with the server side of the RPC mechanism.
Some of them are called by the server side dispatch function. Others,
such as svc_run(), are called when the server is initiated.

Because the service transport handle SVCXPRT contains a single data area for
decoding arguments and encoding results, the structure cannot freely be shared between
threads that call functions to decode arguments and encode results. When a
server is operating in the Automatic or User MT modes, however, a copy
of this structure is passed to the service dispatch procedure in order
to enable concurrent request processing. Under these circumstances, some routines which would
otherwise be Unsafe, become Safe. These are marked as such. Also marked
are routines that are Unsafe for multithreaded applications, and are not to be
used by such applications. See rpc(3NSL) for the definition of the SVCXPRT
data structure.

The svc_dg_enablecache() function allocates a duplicate request cache for the service endpoint
xprt, large enough to hold cache_size entries. Once enabled, there is no
way to disable caching. The function returns 1 if space necessary for
a cache of the given size was successfully allocated, and 0 otherwise.
This function is Safe in multithreaded applications.

The svc_done() function frees resources allocated to service a client request directed
to the service endpoint xprt. This call pertains only to servers executing
in the User MT mode. In the User MT mode, service procedures
must invoke this call before returning, either after a client request has been
serviced, or after an error or abnormal condition that prevents a reply
from being sent. After svc_done() is invoked, the service endpoint xprt should
not be referenced by the service procedure. Server multithreading modes and parameters can
be set using the rpc_control() call. This function is Safe in multithreaded
applications. It will have no effect if invoked in modes other than
the User MT mode.

The svc_exit() function when called by any of the RPC server procedures
or otherwise, destroys all services registered by the server and causes svc_run()
to return. If RPC server activity is to be resumed, services must
be reregistered with the RPC library either through one of the rpc_svc_create(3NSL) functions,
or using xprt_register(3NSL). The svc_exit() function has global scope and ends all
RPC server activity.

The svc_freeargs() function macro frees any data allocated by the RPC/XDR system
when it decoded the arguments to a service procedure using svc_getargs(). This
routine returns TRUE if the results were successfully freed, and FALSE otherwise. This
function macro is Safe in multithreaded applications utilizing the Automatic or User
MT modes.

The svc_getargs() function macro decodes the arguments of an RPC request associated
with the RPC service transport handle xprt. The parameter in is the
address where the arguments will be placed; inproc is the XDR routine used
to decode the arguments. This routine returns TRUE if decoding succeeds, and
FALSE otherwise. This function macro is Safe in multithreaded applications utilizing the Automatic
or User MT modes.

The svc_getreq_common() function is called to handle a request on a file
descriptor.

The svc_getreq_poll() function is only of interest if a service implementor does
not call svc_run(), but instead implements custom asynchronous event processing. It is
called when poll(2) has determined that an RPC request has arrived on
some RPC file descriptors; pollretval is the return value from poll(2) and
pfdp is the array of pollfd structures on which the poll(2) was done.
It is assumed to be an array large enough to contain the
maximal number of descriptors allowed. The svc_getreq_poll() function macro is Unsafe in
multithreaded applications.

The svc_getreqset() function is only of interest if a service implementor does
not call svc_run(), but instead implements custom asynchronous event processing. It is
called when select(3C) has determined that an RPC request has arrived on
some RPC file descriptors; rdfds is the resultant read file descriptor bit
mask. The routine returns when all file descriptors associated with the value of
rdfds have been serviced. This function macro is Unsafe in multithreaded applications.

The svc_getrpccaller() function is the approved way of getting the network address
of the caller of a procedure associated with the RPC service transport
handle xprt. This function macro is Safe in multithreaded applications.

The svc_run() function never returns. In single-threaded mode, the function waits for
RPC requests to arrive. When an RPC request arrives, the svc_run() function
calls the appropriate service procedure. This procedure is usually waiting for the poll(2)
library call to return.

Applications that execute in the Automatic or the User MT mode should
invoke the svc_run() function exactly once. In the Automatic MT mode, the
svc_run() function creates threads to service client requests. In the User MT
mode, the function provides a framework for service developers to create and manage
their own threads for servicing client requests.

The svc_fdset global variable reflects the RPC server's read file descriptor bit
mask. This is only of interest if service implementors do not call
svc_run(), but rather do their own asynchronous event processing. This variable is read-only
may change after calls to svc_getreqset() or after any creation routine. Do
not pass its address to select(3C). Instead, pass the address of a copy.
multithreaded applications executing in either the Automatic MT mode or the user
MT mode should never read this variable. They should use auxiliary threads
to do asynchronous event processing. The svc_fdset variable is limited to 1024
file descriptors and is considered obsolete. Use of svc_pollfd is recommended instead.

The svc_pollfd global variable points to an array of pollfd_t structures that
reflect the RPC server's read file descriptor array. This is only of
interest if service service implementors do not call svc_run() but rather do their
own asynchronous event processing. This variable is read-only, and it may change
after calls to svc_getreg_poll() or any creation routines. Do no pass its
address to poll(2). Instead, pass the address of a copy. By default,
svc_pollfd is limited to 1024 entries. Use rpc_control(3NSL) to remove this limitation.
multithreaded applications executing in either the Automatic MT mode or the user
MT mode should never be read this variable. They should use auxiliary
threads to do asynchronous event processing.

The svc_max_pollfd global variable contains the maximum length of the svc_pollfd array.
This variable is read-only, and it may change after calls to svc_getreg_poll()
or any creation routines.

The svc_sendreply() function is called by an RPC service dispatch routine to
send the results of a remote procedure call. The xprt parameter is
the transport handle of the request. The outproc parameter is the XDR routine
used to encode the results. The out parameter is the address of
the results. This routine returns TRUE if it succeeds, FALSE otherwise. The
svc_sendreply() function macro is Safe in multithreaded applications that use the Automatic or
the User MT mode.

The svc_fd_negotiate_ucred() function is called by an RPC server to inform the
underlying transport that the function wishes to receive ucreds for local calls,
including those over IP transports.

The svc_getcallerucred() function attempts to retrieve the ucred_t associated with the caller.
The function returns 0 when successful and -1 when not.

When successful, the svc_getcallerucred() function stores the pointer to a freshly allocated
ucred_t in the memory location pointed to by the ucred argument if
that memory location contains the null pointer. If the memory location is non-null,
the function reuses the existing ucred_t. When ucred is no longer needed,
a credential allocated by svc_getcallerucred() should be freed with ucred_free(3C).

Attributes

The svc_fd_negotiate_ucred(), svc_dg_enablecache(), svc_getrpccaller(), and svc_getcallerucred() functions are Safe in multithreaded applications.
The svc_freeargs(), svc_getargs(), and svc_sendreply() functions are Safe in multithreaded applications that use
the Automatic or the User MT mode. The svc_getreq_common(), svc_getreqset(), and svc_getreq_poll()
functions are Unsafe in multithreaded applications and should be called only from the
main thread.